[evlatests] WIDAR P-band status update: 13SEP2014

[Huib Intema (NRAO)]

Hi Dan,

Thanks for the list; I'm happy to see most things confirmed. Hopefully 
we'll run a P-band test this afternoon, so I can verify the EA11 fix.

The ripples on EA08 and EA13 have gone mostly unnoticed so far because 
their frequency width is close to the 16 MHz spectral window width with 
which we observe in P-band (16 x 16MHz). The ripples are clearly there, 
but may be somewhat more difficult to see these in the plots you use.

-- Huib


On 18-Sep-14 11:58, Dan Mertely wrote:
> Thanks Huib.  Here is my review, taken from previous maintenance
> action notes, and this week's all-antenna bandpass plot analysis
> (\\filehost\evla\techdocs\rfi\rfi-survey\plots\evla-bandpass\p-band\20140916-all). 
>
>
> 1)  ea20: yes, we fixed a cabling problem up at the apex.
> 2)  ea23: yes, we fixed a cabling problem up at the apex.
> 3)  ea04: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant 
> checkout.
> 4)  ea06: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant 
> checkout.
> 5)  ea08: bandpasses look OK.
> 6)  ea11: dipole was rotated.  Pol s/b OK. How are the amps?
> 7)  ea13: bandpasses look OK.
> 8)  ea14: LXV side has weak RFI SNR at low end.
> 9)  ea16: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant 
> checkout.
> 10) ea17: RYH side has 80 MHz ripple, weak RFI SNR.  Needs on ant 
> checkout.
> 11) ea18: has odd image and noise on IFD.
> 12) ea19: has odd image and noise on IFA & IFC
>
> -Mert
>
>
>
>
> On 9/16/2014 2:38 PM, Huib Intema (NRAO) wrote:
>> Dear P-banders,
>>
>> Here is the combined outcome of two short VLA WIDAR P-band status 
>> tests (few
>> minutes on 3C48) we ran on Sept 5 and 13. EA26 was out in both. Major 
>> points of
>> attention are:
>>
>> + EA20 no longer shows the huge bandpass ripple on LCP (thanks for 
>> the fix!)
>>
>> ~ EA23 no longer shows the large bandpass ripple on RCP
>>    Was this fixed or is this intermittent?
>>
>> - EA04 has very low gain in RCP, and low gain in LCP
>> - EA08 has large bandpass ripple in LCP
>> - EA11 has either loose / rotated feed, or swapped polarizations + huge
>> polarization leakage
>> - EA13 has large bandpass ripple in LCP
>> - EA14 has low gain in RCP
>> - EA16 has low gain and erratic bandpass in RCP (Sept 13 only)
>> - EA17 has swapped polarizations and low gain in LCP (after software 
>> swap)
>> - EA18 has low gain in RCP
>> - EA19 has low gain in RCP
>> - EA28 has fast bandpass ripple on LCP
>>
>> -- Huib
>>
>>
>>
>> I've used the same analysis approach as previously, therefore can be 
>> interpreted
>> in the same way. Antenna EA26 was not in the array. The following 
>> polarization
>> labeling convention applies: RCP = horizontal dipole(s), LCP = 
>> vertical dipole(s).
>>
>> * Swapped polarizations:
>> - EA11 (or possibly a rotated feed)
>> - EA17 (after the dipole fix)
>>
>> * Antenna power levels (determined from gain calibration):
>> Most antennas have similar (healthy) power levels, within ~30 percent 
>> of the
>> median, except:
>> - EA04 RCP: P = 0.05
>> - EA04 LCP: P = 0.40
>> - EA14 RCP: P = 0.35
>> - EA16 RCP: P = 0.35
>> - EA18 RCP: P = 0.45
>> - EA19 RCP: P = 0.45
>> (P = power level relative to median)
>>
>> * Bandpass ripples (determined from bandpass calibration):
>> Most antennas have (healthy) smooth bandpass amplitude structure and 
>> linear
>> phase structure across frequency (224-480 MHz; ignoring the ranges 
>> with known
>> RFI), except:
>> - EA02 RCP: A = 0.15, F = 5.9 MHz, L = 25.5 m
>> - EA02 LCP: A = 0.15, F = 6.2 MHz, L = 24.0 m
>> - EA08 LCP: A = 0.30, F = 17. MHz, L = 8.7 m
>> - EA13 LCP: A = 0.35, F = 20. MHz, L = 7.5 m
>> - EA14 RCP: possible large ripple, F ~ 75. MHz, L = 2.0 m
>> - EA16 RCP: erratic bandpass
>> - EA17 LCP: upturn in upper 1/4th of the band
>> - EA28 LCP: A = 0.25, F = 3.6 MHz, L = 42.0 m
>> (A = relative ripple peak-peak amplitude, F = the ripple frequency 
>> width , L =
>> associated cable length)
>>
>> * Polarization leakage (determined from a single, RFI-free 16 MHz 
>> subband):
>> Most antennas show a non-zero (0.10-0.15, or 10-15 percent) amplitude 
>> in the
>> crosshand correlations RL and LR, except:
>> - EA11: A = 0.42(!)
>> (A = polarization leakage, relative to the parallel hand signal)
>>
>>
>>
>>
>>
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